Question 468 of 1,819
IP RoutingmediumMatchingObjective-mapped

OSPF Neighbor States — Down, Init, 2-Way, ExStart, Exchange, Loading, Full

This 200-301 practice question tests your understanding of ip routing. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

Drag and drop the OSPFv2 neighbor states on the left to the correct descriptions on the right.

Quick Answer

The correct answer pairs Down with “No Hello packets received from the neighbor,” because the OSPF neighbor state machine begins when a router has not yet detected any OSPF Hello packets from a potential neighbor. This progression is fundamental to OSPF adjacency formation: after Down, the router moves to Init upon seeing a Hello, then to 2-Way when bidirectional communication is confirmed, followed by ExStart for master/slave election, Exchange for Database Description packets, Loading for requesting missing LSAs via LSR/LSU, and finally Full when LSDBs are synchronized. On the CCNA 200-301 v2 exam, this drag-and-drop question tests your ability to map each state to its precise trigger, often with traps like confusing ExStart (election) with Exchange (DBD transmission) or mixing up Loading and Full. A common memory tip is the mnemonic “DIE-ELF” — Down, Init, 2-Way, ExStart, Exchange, Loading, Full — which helps you recall the order and focus on the key action at each step: no Hello, Hello seen, bidirectional, election, DBD, LSR/LSU, and synchronized.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

Down: No Hello packets received from the neighbor.

OSPF neighbor states progress: Down (no Hello), Init (Hello seen), 2-Way (bidirectional), ExStart (master/slave election), Exchange (DBD packets), Loading (requesting missing LSAs via LSR/LSU), Full (LSDB synchronized). These states ensure proper adjacency formation and reliable database exchange.

Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • Down: No Hello packets received from the neighbor.

    Why this is correct

    This is correct because the Down state is the initial OSPF state where no Hello packets have been received from the neighbor, indicating no communication.

    Related concept

    OSPF neighbours must agree on key parameters.

  • Init: Hello packets received, but neighbor's Router ID not seen in Hello.

    Why it's wrong here

    This is incorrect because in the Init state, the router has received a Hello packet from the neighbor, but the neighbor's Router ID is not yet seen in the Hello packet's neighbor list.

  • 2-Way: Bidirectional communication established; both routers see each other in Hello packets.

    Why it's wrong here

    This is incorrect because the 2-Way state is indeed when bidirectional communication is established, but the question asks for the correct description of the Down state.

  • ExStart: Master/slave election occurs; first DD packets exchanged.

    Why it's wrong here

    This is incorrect because ExStart is the state where master/slave election happens and initial DD packets are exchanged, not the Down state.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.

Down: No Hello packets received from the neighbor.Correct answer

Why this is correct

This is correct because the Down state is the initial OSPF state where no Hello packets have been received from the neighbor, indicating no communication.

Init: Hello packets received, but neighbor's Router ID not seen in Hello.Wrong answer — click to see why

Why this is wrong here

The Init state is actually when a Hello packet is received, but the router's own Router ID is not in the neighbor's Hello packet; the neighbor's Router ID is seen.

Why candidates choose this

Candidates often confuse whether the neighbor's Router ID is seen or not; they may think Init means the neighbor's ID is not yet known.

2-Way: Bidirectional communication established; both routers see each other in Hello packets.Wrong answer — click to see why

Why this is wrong here

The 2-Way state is a valid OSPF state, but it does not match the description for Down; it describes a different state.

Why candidates choose this

Candidates may incorrectly match the description of 2-Way to Down if they confuse the sequence of states.

ExStart: Master/slave election occurs; first DD packets exchanged.Wrong answer — click to see why

Why this is wrong here

ExStart is a later state in OSPF adjacency formation, not the initial Down state.

Why candidates choose this

Candidates might think that the first state involves some exchange, but Down is the very beginning with no communication.

Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

Common exam traps

Common exam trap: OSPF can fail even when IP connectivity looks correct

OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.

Detailed technical explanation

How to think about this question

OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.

KKey Concepts to Remember

  • OSPF neighbours must agree on key parameters.
  • Router ID selection can affect neighbour relationships and LSDB output.
  • OSPF cost influences the preferred path.
  • A route can appear in OSPF information but not become the installed route.

TExam Day Tips

  • Check area mismatch first when OSPF adjacency fails.
  • Review passive interfaces when a network is advertised but no neighbour forms.
  • Use show ip ospf neighbor and show ip route clues carefully.

Key takeaway

OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.

Real-world example

How this comes up in practice

A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.

Visual reference

R1 R2 R3 R4 10 100 10 100 OSPF picks R1→R2→R4 (cost 20) over R1→R3→R4 (cost 200)

Quick reference

Routing Protocol Comparison

ProtocolMetricMax HopsAlgorithmType
RIP v2Hop count15Bellman-FordDistance vector
OSPFCost (bandwidth)UnlimitedDijkstra (SPF)Link state
EIGRPComposite metricUnlimitedDUALHybrid
IS-ISCostUnlimitedDijkstraLink state
BGPPolicy / attributesUnlimitedPath vectorPath vector

RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.

What to study next

Got this wrong? Here's your next step.

Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 200-301 OSPF questions on adjacency and route selection.

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FAQ

Questions learners often ask

What does this 200-301 question test?

IP Routing — This question tests IP Routing — OSPF neighbours must agree on key parameters..

What is the correct answer to this question?

The correct answer is: Down: No Hello packets received from the neighbor. — OSPF neighbor states progress: Down (no Hello), Init (Hello seen), 2-Way (bidirectional), ExStart (master/slave election), Exchange (DBD packets), Loading (requesting missing LSAs via LSR/LSU), Full (LSDB synchronized). These states ensure proper adjacency formation and reliable database exchange.

What should I do if I get this 200-301 question wrong?

Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 200-301 OSPF questions on adjacency and route selection.

What is the key concept behind this question?

OSPF neighbours must agree on key parameters.

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Last reviewed: Jun 6, 2026

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